The present invention relates to medical devices, and in particular to devices for creating lumens in totally occluded vessels.
Balloon angioplasty and rotational ablation are two commonly performed, minimally invasive surgical techniques used to create lumens in a patient""s occluded blood vessel. With these techniques, a guide catheter is usually inserted into the patient""s femoral artery and routed through the vasculature to the point of an occlusion. Next, a guide wire is inserted through the guide catheter and advanced to a point past the occlusion. A treatment device, either an angioplasty balloon or a rotational ablation device, is then run over the guide wire to compress or remove the occluding material from the vessel. While these minimally invasive procedures often eliminate the need to perform more invasive surgery, the procedures are not often used when a patient""s vessel is totally occluded because the guide wire cannot be advanced past the occlusion. Therefore, the majority of total occlusions still are treated using more invasive surgical techniques.
Given the benefits associated with less invasive atherectomy procedures, there is a need to adapt these minimally invasive, percutaneous procedures to the situation where a vessel is totally occluded.
The present invention is a technique for guiding a cutting device through a total vascular occlusion without perforating a vessel wall. An eccentric cutter is supplied with a high frequency electronic signal for use in determining the impedance between the cutter and a number of wire electrodes disposed proximally of the cutter.
In the embodiment, the proximal electrodes are formed as an expandable wire stent wherein the tips of the wires engage but do not perforate the surrounding vessel wall. The impedance between the eccentric cutter and each of the electrodes is determined as the cutter is advanced through the occlusion. Cutting proceeds until the cutter engages the vessel wall and the impedance between the eccentric cutter and the proximal electrodes decreases. At this time, the direction of the eccentric cutter is changed and cutting continues along the length of the total occlusion.
In accordance with another aspect of the present invention, carbon dioxide is delivered to the cutting area to remove blood between the cutter and the proximal electrodes.
In yet another embodiment of the invention, a low level pacing signal is supplied to the cutter end and it is determined if the pacing signal captures the heart. If no capture occurs, the cutter is advanced. Once capture occurs, the direction of the cutter is changed.